Highly ordered anodic TiO2 nanotube arrays fabricated by electrochemical anodization were sensitized with ruthenium dye N-719 to yield dye-sensitized TiO2 nanotube solar cells. Rational surface treatments on photoanode TiO2 nanotubes markedly improved the device performance. With TiCl4 treatment, in conjunction with oxygen plasma exposure under optimized conditions, dye-sensitized TiO2 nanotube solar cells produced using 14-μm-thick TiO2 nanotube arrays in backside illumination mode subjected to simulated AM 1.5 G irradiation of 100 mW/cm2 exhibited a pronounced power conversion efficiency (PCE) of 7.37%.

Isoreticular principle has been employed to realize a flexible-robust metal–organic framework (MOF) with extended pore structure for the adsorptive removal of trace acetylene from ethylene under ambient conditions. The substitution from zinc­(II) to copper­(II) of high coordination distortion leads to elongated Cu–F bonds that expand the closed pore cavities in the prototypical MOF from 3.5 × 3.9 × 4.1 to 3.6 × 4.3 × 4.2 Å3. The optimal cavity size together with strong binding sites thus endows the new Cu analogue to possess open pore space accessible for trace C2H2 within a substantial low-pressure range while excluding C2H4 molecules, as validated by gas isotherms and single-crystal structure of its partially C2H2-loading phase. In contrast to the Zn prototype, at 298 K and 1.0 bar, the guest-free Cu analogue shows significant C2H2 uptake increase with a total capacity of 4.57 mmol g–1, and gains an over two orders of magnitude jump in IAST selectivity for C2H2/C2H4 (1/99, v/v). These results are higher than the benchmark MOFs for molecular sieving of C2H2/C2H4, leading a high C2H4 productivity of 14.9 mmol g–1. Crystallography studies, molecular modeling, selectivity evaluation, and breakthrough experiments have comprehensively demonstrated this flexible-robust MOF as an efficient adsorbent for C2H2/C2H4 separation.

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Selective elimination of sulfur dioxide is significant in flue gas desulfurization and natural gas purification, yet developing adsorbents with high capture capacity especially at low partial pressure as well as excellent cycling stability remains a challenge. Herein, a family of isostructural gallate-based MOFs with abundant hydrogen bond donors decorating the pore channel was reported for selective recognition and dense packing of sulfur dioxide via multiple hydrogen bonding interactions. Multiple O···H–O hydrogen bonds and O···H–C hydrogen bonds guarantee SO2 molecules are firmly grasped within the framework, and appropriate pore apertures afford dense packing of SO2 with high uptake and density up to 1.86 g cm–3, which is evidenced by dispersion-corrected density functional theory calculations and X-ray diffraction resolution of a SO2-loaded single crystal. Ultrahigh adsorption uptake of SO2 at extremely low pressure (0.002 bar) was achieved on Co-gallate (6.13 mmol cm–3), outperforming all reported state-of-the-art MOFs. Record-high IAST selectivity of SO2/CO2 (325 for Mg-gallate) and ultrahigh selectivity of SO2/N2 (>1.0 × 104) and SO2/CH4 (>1.0 × 104) were also realized. Breakthrough experiments further demonstrate the excellent removal performance of trace amounts of SO2 in a deep desulfurization process. More importantly, M-gallate shows almost unchanged breakthrough performance after five cycles, indicating the robust cycling stability of these MOFs.

TiO 2 nanostructures, including nanowires, highly ordered nanotube arrays, and single crystalline nanoplates, were obtained from electrochemically anodized Ti foil in a fluorine-containing ethylene glycol electrolyte. The TiO 2 nanowires, formed by the electric field induced chemical splitting of TiO 2 nanotubes by fluoride ions during a lengthy anodization can be isolated from the nanotube arrays by mild ultrasonication. The highly ordered TiO 2 nanotubes buried underneath are thus exposed. The transformation of as-prepared amorphous TiO 2 nanotubes into the anatase or rutile phase as a function of annealing temperature was systematically scrutinized by Raman spectroscopic measurements in conjunction with TEM imaging. In the latter study, the ultramicrotomed sections of the samples clearly exhibited the formation of highly crystalline TiO 2 . More importantly, crystalline TiO 2 nanotubes were mechanically broken into intriguing single crystalline TiO 2 nanoplates as a result of ultramicrotoming. The present study not only demonstrates a facile approach to produce high quality TiO 2 nanowires, nanotubes, and nanoplates in a simple manner, but also provides valuable insights into temperature dependent crystalline transformation in the anodic TiO 2 nanotube arrays.